1. Field of the Invention
The present invention relates to an image forming apparatus, more specifically an image forming apparatus including an image reading apparatus.
2. Description of the Related Art
Conventionally, an image reading apparatus such as a scanner or an image forming apparatus such as a copy machine and facsimile use a document conveyance apparatus that conveys a plurality of documents sheet-by-sheet. The document conveyance apparatus reads a document with a fixed reading sensor according to position information obtained from a detecting unit that is provided in a document conveyance path to detect leading and trailing edges of the document. The document conveyance apparatus discussed in Japanese Patent Application Laid-Open No. 7-196181 detects an interval between the document being read and the next document, and actively controls the interval to be predetermined length. In the document conveyance apparatus discussed in Japanese Patent Application Laid-Open No. 7-251981, an interval between the document being read and the next document is set to be wider than an interval between the position where the reading sensor reads the document and the position where leading and trailing edges of the document are detected.
However, the document conveyance apparatus discussed in Japanese Patent Application Laid-Open No. 7-196181 requires a plurality of drive sources, thus cannot be realized with a single drive source. Furthermore, the document conveyance apparatus discussed in Japanese Patent Application Laid-Open No. 7-196181 cannot shorten a conveyance interval more than prescribed in order to secure an interval between a document and a subsequent document even when the document interval varies.
Even if the aforementioned mechanism operates to convey the document at a constant interval, an interval between the documents varies. For example, a roller that conveys the documents can slip and cause variation in the amount of the documents pulled out when the document is fed.